diff --git a/ex03.ipynb b/ex03.ipynb
index 32ce950..99c13cf 100644
--- a/ex03.ipynb
+++ b/ex03.ipynb
@@ -34,7 +34,7 @@
       },
       "source": [
         "# EX. 3\n",
-        "[Colab.] https://colab.research.google.com/drive/1-akVG4V9HGUE1ZjNOAy-eZLKxkRUb0Kz#scrollTo=VHqOrojPQLcu"
+        "[Colab.] https://github.com/Seong-heum/kics2021/blob/main/ex03.ipynb"
       ]
     },
     {
@@ -49,7 +49,7 @@
       "source": [
         "!pip install opencv-contrib-python==4.4.0.44"
       ],
-      "execution_count": 1,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "stream",
@@ -94,7 +94,7 @@
         "from google.colab.patches import cv2_imshow\n",
         "print(cv.__version__)"
       ],
-      "execution_count": 2,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "stream",
@@ -117,7 +117,7 @@
       "source": [
         "!wget https://www.dropbox.com/s/9bkst33ad79ckvv/baboon.jpg?dl=0 -O baboon.jpg"
       ],
-      "execution_count": 3,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "stream",
@@ -161,7 +161,7 @@
         "img = cv.imread(\"baboon.jpg\")\n",
         "cv2_imshow(img)"
       ],
-      "execution_count": 4,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "display_data",
@@ -193,7 +193,7 @@
         "cv2_imshow(G)\n",
         "cv2_imshow(R)"
       ],
-      "execution_count": 5,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "display_data",
@@ -247,7 +247,7 @@
         "ext = cv.inRange(img, (0, 0, 200), (100, 100, 255)) # segmentation\n",
         "cv2_imshow(ext)"
       ],
-      "execution_count": 6,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "display_data",
@@ -286,7 +286,7 @@
         "    out = np.flipud(out)\n",
         "    return out"
       ],
-      "execution_count": 7,
+      "execution_count": null,
       "outputs": []
     },
     {
@@ -304,7 +304,7 @@
         "lines = hist_lines(img)\n",
         "cv2_imshow(lines)"
       ],
-      "execution_count": 8,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "display_data",
@@ -340,7 +340,7 @@
         "cv2_imshow(lines_eq)\n",
         "cv2_imshow(img_eq)"
       ],
-      "execution_count": 10,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "display_data",
@@ -396,7 +396,7 @@
         "img[dst > 0.01 * dst.max()] = [0, 0, 255]\n",
         "cv2_imshow(img)\n"
       ],
-      "execution_count": 11,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "stream",
@@ -460,7 +460,7 @@
         "!wget https://www.dropbox.com/s/27rvsjfjhnwp6jd/box.png?dl=0 -O box.png\n",
         "!wget https://www.dropbox.com/s/muxbttnq26815qy/box_in_scene.png?dl=0 -O box_in_scene.png"
       ],
-      "execution_count": 12,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "stream",
@@ -520,7 +520,7 @@
         "img0 = cv.imread(\"box.png\", cv.IMREAD_GRAYSCALE)\n",
         "img1 = cv.imread(\"box_in_scene.png\", 0)"
       ],
-      "execution_count": 13,
+      "execution_count": null,
       "outputs": []
     },
     {
@@ -537,7 +537,7 @@
         "#kp0, des0 = orb.detectAndCompute(img0, None)\n",
         "#kp1, des1 = orb.detectAndCompute(img1, None)"
       ],
-      "execution_count": 14,
+      "execution_count": null,
       "outputs": []
     },
     {
@@ -550,7 +550,7 @@
         "bf = cv.BFMatcher(cv.DescriptorMatcher_BRUTEFORCE, crossCheck=False)\n",
         "pairs_of_matches = bf.knnMatch(des0, des1, k=2)"
       ],
-      "execution_count": 15,
+      "execution_count": null,
       "outputs": []
     },
     {
@@ -564,7 +564,7 @@
         "pairs_of_matches = sorted(pairs_of_matches, key=lambda x:x[0].distance)\n",
         "img_pairs_of_matches = cv.drawMatchesKnn( img0, kp0, img1, kp1, pairs_of_matches[:20], img1, flags=cv.DRAW_MATCHES_FLAGS_NOT_DRAW_SINGLE_POINTS)"
       ],
-      "execution_count": 16,
+      "execution_count": null,
       "outputs": []
     },
     {
@@ -582,7 +582,7 @@
         "plt.imshow(img_pairs_of_matches)\n",
         "plt.show()"
       ],
-      "execution_count": 17,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "display_data",
@@ -608,7 +608,7 @@
         "# Apply the ratio test.\n",
         "matches = [x[0] for x in pairs_of_matches if len(x) > 1 and x[0].distance < 0.8 * x[1].distance]"
       ],
-      "execution_count": 18,
+      "execution_count": null,
       "outputs": []
     },
     {
@@ -620,7 +620,7 @@
         "# Draw the best 20 matches.\n",
         "img_matches = cv.drawMatches( img0, kp0, img1, kp1, matches[:20], img1, flags=cv.DRAW_MATCHES_FLAGS_NOT_DRAW_SINGLE_POINTS)"
       ],
-      "execution_count": 19,
+      "execution_count": null,
       "outputs": []
     },
     {
@@ -638,7 +638,7 @@
         "plt.imshow(img_matches)\n",
         "plt.show()"
       ],
-      "execution_count": 20,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "display_data",
@@ -674,7 +674,7 @@
         "import cv2 as cv\n",
         "from matplotlib import pyplot as plt"
       ],
-      "execution_count": 21,
+      "execution_count": null,
       "outputs": []
     },
     {
@@ -690,7 +690,7 @@
         "!wget https://www.dropbox.com/s/oj0mfo6e654c9s2/tsukuba_l.png?dl=0 -O tsukuba_l.png\n",
         "!wget https://www.dropbox.com/s/0pe324puqcd6o7e/tsukuba_r.png?dl=0 -O tsukuba_r.png"
       ],
-      "execution_count": 22,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "stream",
@@ -756,7 +756,7 @@
         "cv2_imshow(imgL)\n",
         "cv2_imshow(imgR)"
       ],
-      "execution_count": 23,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "display_data",
@@ -800,7 +800,7 @@
         "plt.imshow(disparity,'gray')\n",
         "plt.show()"
       ],
-      "execution_count": 24,
+      "execution_count": null,
       "outputs": [
         {
           "output_type": "display_data",